[PATCH 1/2] y2038: Helper macro to convert struct __timespec64 to struct timespec

[Lukasz Majewski <lukma@denx.de>]

This macro allows conversion between Y2038 safe struct __timespec64 and
struct timespec.
The struct __timespec64's tv_nsec field is checked if it is in the correct
range.
Moreover, the tv_sec is asserted if it fits into the time_t range.
When error is detected the errno is set accordingly and the function, which
uses this macro returns -1.

Tested with scripts/build-many-glibcs.py script.
---
 include/time.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/include/time.h b/include/time.h
index d93b16a781..c2b6c9b842 100644
--- a/include/time.h
+++ b/include/time.h
@@ -236,5 +236,28 @@ valid_timespec64_to_timeval (const struct __timespec64 ts64)
 
   return tv;
 }
+
+/* Check if a value lies with the valid nanoseconds range.  */
+#define IS_VALID_NANOSECONDS(ns) ((ns) >= 0 && (ns) <= 999999999)
+
+/* Check and convert a struct __timespec64 into a struct timespec.
+   This macro checks if the valid number of nanoseconds has been provided
+   by ts64 and if not the errno is set to EINVAL and -1 is returned.
+   Moreover, the number of seconds is check as well, if it is in the time_t
+   range. If not the errno is set to EOVERFLOW and -1 is returned.  */
+#define timespec64_to_timespec(ts64)                                           \
+  ({                                                                           \
+    if (! IS_VALID_NANOSECONDS (ts64.tv_nsec))                                 \
+      {                                                                        \
+        __set_errno (EINVAL);                                                  \
+        return -1;                                                             \
+      }                                                                        \
+    if (! in_time_t_range (ts64.tv_sec))                                       \
+      {                                                                        \
+        __set_errno (EOVERFLOW);                                               \
+        return -1;                                                             \
+      }                                                                        \
+    valid_timespec64_to_timespec (ts64); })
+
 #endif
 #endif
-- 
2.20.1